cmd/ld: skip 0-length write in cwrite

The 0-length part is fine, but some callers that write 0 bytes
also pass nil as the data pointer, and the Plan 9 kernel kills the
process with 'invalid address in sys call' in that case.

R=ken2
CC=golang-dev
https://golang.org/cl/6862051

diff --git a/src/cmd/ld/lib.c b/src/cmd/ld/lib.c
index 8e3a8dd690fb9b6344168672dfc5aec3b634836e..0f51e6b9f270c1fffaee16f5a8a22d44f232164f 100644 (file)
--- a/src/cmd/ld/lib.c
+++ b/src/cmd/ld/lib.c
@@ -1493,6 +1493,8 @@ void
 cwrite(void *buf, int n)
 {
        cflush();
+       if(n <= 0)
+               return;
        if(write(cout, buf, n) != n) {
                diag("write error: %r");
                errorexit();